SPECTROPHOTOMETRIC REACTION-RATE METHOD FOR THE DETERMINATION OF SULFIDE BY CATALYTIC ACTION ON THE OXIDATION OF SODIUM-AZIDE BY IODINE

A catalytic kinetic method has been used for the determination of ultra trace amounts of total dissolved sulfide based on its catalytic effect on the reaction between sodium azide and iodine in aqueous solution. Sulfide over the range of 0.020-0.500 mu g.ml(-1) was determined spectrophotometrically by measuring the decrease in absorbance of iodine at 348 nm by the fixed-time method. The decrease in absorbance during the first 0.5-3.0 min from initiation of the reaction is related to the concentration of sulfide. The detection limit is 0.010 mu g.ml(-1). The relative standard deviation for the determination of 0.050 mu g.ml-1 of sulfide was 2.2%. The proposed method was successfully applied for the determination of sulfide in synthetic samples, spring water and of sulfur in steel.